JP2000030871A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a nonluminescence section in a luminescence area and to keep the luminescence area at the same state as the initial state over a long period. SOLUTION: An anode 2 made of a transparent conductive film and having through holes 4 to form the pattern of a luminescence pattern 3 is provided on an element substrate 1 made of a glass substrate. Insulating layers 15 including water catching materials 16 are formed on the anode 2 to bury the through holes and cover the edge portions 4 a of the through holes 4. Organic layers 6 are laminated on the anode 2 and the insulating layers 15, and a cathode 7 made of a metal thin film is laminated on the organic layers 6. A seal substrate 8 is sealed to the outer peripheral edge portion of the element substrate 1 to seal the inert gas G by dry nitrogen in it. The insulating layers 15 are made of a polyimide film spin-coated and heat-treated with a polyimide solution mixed and dispersed with the water catching material 16 on the anode 2. The water catching material 16 is made of calcium oxide or barium oxide adsorbing and retaining moisture via the chemical reaction to water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (hereinafter abbreviated as an organic EL device) in which a thin film of an organic compound material is laminated between a pair of electrodes at least one of which is a transparent electrode.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin film containing a fluorescent organic compound is sandwiched between a cathode and an anode, and holes and electrons are injected into the thin film and recombined to form excitons. An exciton is generated, and display is performed using light emission (fluorescence / phosphorescence) when the exciton is deactivated.

FIG. 2 is a side sectional view showing the structure of a general organic EL device of this type. The organic EL device shown in FIG.
An element substrate 1 made of a glass substrate having an insulating property and a light transmitting property is used as a base. An anode 2 made of a transparent conductive film is formed on the element substrate 1. The anode 2 made of a transparent conductive film is formed on the element substrate 1 with a through hole 4 so as to form a pattern of the light emitting area 3.

An insulating layer 5 made of a polyimide film is formed in a through hole 4 of the anode 2 made of a transparent conductive film.
The insulating layer 5 forms the pattern of the light emitting area 3 and covers minute projections of the edge portion 4a of the through hole 4 generated at the time of patterning the anode 2 by the transparent conductive film. Short circuit between electrodes is prevented.

As shown in FIG. 2, an organic layer 6 made of a thin film of an organic compound material is laminated on the anode 2. FIG.
The organic layer 6 is formed of a copper phthalocyanine (CuPc) organic film 6a as a hole injection layer, and a Bi as a hole transport layer.
It has a three-layer structure of an organic film 6b of s (N- (1-naphyl) -N-phneyl) benzidine (α-NPD) and an aluminum quinoline (Alq ₃ ) organic film 6c as an emission layer and an electron transport layer, A light emitting area 3 is formed.

As shown in FIG. 2, a cathode 7 made of a metal thin film of an Al: Li alloy is formed on the organic layer 6 (Alq ₃ organic film 6c). A sealing substrate 8 as a sealing member is fixed to an outer peripheral portion of the element substrate 1 with an adhesive,
A package 9 is configured. Inside the package 9,
Dry air or an inert gas (for example, dry nitrogen) G is sealed.

In the organic EL device, when a voltage is applied between the anode 2 and the cathode 7 to cause a constant current to flow, holes are injected from the anode 2 and electrons are injected from the cathode 7 into the organic layer 6. You. Then, the injected holes and electrons are recombined in the organic layer 6 to generate excitons, and a desired display is performed by emission of light when the excitons are deactivated. The luminescence at that time is
It is observed from the element substrate 1 side through the anode 2 made of a transparent conductive film.

[0008] By the way, the organic E constituted as described above is used.
The biggest problem of the L element is to improve the durability. Among them, the generation and growth of a non-light emitting portion called a dark spot is the most important problem. The cause of the dark spot is considered to be the largest effect of moisture and oxygen,
In particular, even a very small amount of water is considered to have a great effect.

[0009] Therefore, a device for removing moisture as much as possible, such as purification of an organic material to be used, quality of a vacuum at the time of film formation, sealing of an element, etc., is implemented, and is manufactured by a dry process. However, at present, sufficient characteristics have not yet been obtained. Even in a commercially available EL display, a large number of dark spots of about 20 μm are generated in the initial stage, which indicates difficulty in countermeasures.

As described above, the biggest problem of the organic EL element is to eradicate dark spots and extend the life.
Significant improvement can be achieved by sealing the element. In addition, improvement is progressing by separately fixing a water catching material to the sealing substrate.

However, in order to put the organic EL element into practical use as a display device, as shown in FIG. 2, an insulating layer 5 made of a polyimide film or the like is formed on the anode 2 in order to enhance the insulation between the anode 2 and the cathode 7. Need to be formed.

Therefore, in the above-described organic EL device shown in FIG. 2, dry nitrogen having a dew point of about -70 ° C. is sealed in the sealing substrate 8 using an adhesive such as an ultraviolet curable resin to prevent dark spots from growing. It employs a sealing structure to suppress it. This structure maintains a dry state and suppresses the generation and growth of dark spots.

[0013]

However, when the organic EL device having the structure shown in FIG. 2 is continuously lit, a non-light emitting portion appears from the boundary between the light emitting area 3 (organic layer 6) and the insulating layer 5, and the light emitting area 3 3 spreads toward the center. The cause is considered to be a trace amount of moisture present in the polyimide film forming the insulating layer 5 in the package 9, and it is presumed that the non-light-emitting portion was induced by the moisture coming into contact with the adhered organic layer 6.

When a non-light-emitting portion appears in the light-emitting area 3 as described above, the light-emitting area of the light-emitting area 3 decreases, and the current density increases. As a result, the voltage applied to the light emitting area 3 rises, causing an overcurrent to flow, possibly damaging the element.

In view of the above, the present invention has been made in view of the above-mentioned problems, and an organic EL device capable of suppressing the occurrence of non-light-emitting portions in a light-emitting area and keeping the light-emitting area in the same state as the initial state for a long time. It is intended to provide an element.

[0016]

In order to achieve the above object, an organic EL device according to a first aspect of the present invention has an element substrate and a through hole so as to form a pattern of a light emitting area. A first electrode made of a conductive film formed thereon, an insulating layer formed on the first electrode so as to fill the through hole and cover an edge portion of the through hole,
An organic layer including a light emitting layer formed on the electrode and the insulating layer; a second electrode formed of a conductive film formed on the organic layer; and An organic EL device comprising a sealing member sealed to an outer peripheral portion of an element substrate, wherein a water catching material is contained in the insulating layer.

According to a second aspect of the present invention, in the organic EL device of the first aspect, at least one of the two electrodes is formed of a conductive film having transparency.

According to a third aspect of the present invention, in the organic EL device according to the first or second aspect, the insulating layer is made of a polyimide film obtained by heat-treating a polyimide solution in which a water catching material is mixed and dispersed.

According to a fourth aspect of the present invention, in the organic EL device according to any one of the first to third aspects, the water catching material is made of calcium oxide or barium oxide.

According to the present invention, the water-absorbing material composed of calcium oxide CaO (or barium oxide BaO) mixed and dispersed in the polyimide film constituting the insulating layer causes a chemical reaction with water to produce calcium hydroxide Ca. (OH) ₂ (or barium hydroxide Ba (OH) ₂ ) is generated to absorb and hold moisture.

[0021]

FIG. 1 is a side sectional view showing an embodiment of an organic EL device according to the present invention. Note that the same components as those of the organic EL element in FIG.

As shown in FIG. 1, the organic EL element is based on an element substrate 1 made of a glass substrate having an insulating property and a light transmitting property. On the element substrate 1, a transparent conductive film made of ITO (Indium Tin Oxide) is formed as a conductive material having transparency. The transparent conductive film can be formed, for example, by PVD (Physical Vapor Depos
)) to form an anode 2 as an electrode. The anode 2 made of a transparent conductive film is formed on the element substrate 1 with a through hole 4 so as to form a pattern of the light emitting area 3. A part of the anode 2 is drawn out to the end of the element substrate 1 and connected to a power supply circuit (not shown).

On the anode 2 made of a transparent conductive film, an insulating layer 15 containing a water catching material 16 is formed so as to fill the through hole 4 and cover the edge 4a of the through hole 4. The insulating layer 15 forms the pattern of the light emitting area 3 and
Covers minute projections at the edge portion 4a of the through hole 4 generated when the anode 2 is patterned by the transparent conductive film, and prevents short circuit between the + and-electrodes (between the anode 2 and the cathode 7) due to electric field concentration at the edge portion 4a. are doing.

The water-absorbing material 16 is made of a non-conductive substance composed of ultrafine particles having a particle size of several μm or less (preferably nano-sized), for example, calcium oxide (CaO), barium oxide (Ba).
O). The water catching material 16 maintains a state of absorbing water by chemical adsorption.

More specifically, when the water catching material 16 is made of calcium oxide CaO, CaO chemically reacts with water to produce calcium hydroxide Ca (OH) _2, and the produced calcium hydroxide Ca (OH) ₂ is retained to adsorb moisture. Similarly, the water catching material 16 is made of barium oxide Ba.
Even in the case of being composed of O, barium oxide BaO retains barium hydroxide Ba (OH) ₂ generated by a chemical reaction with water to adsorb water.

The insulating layer 15 containing the water catching material 16
The water catching material 16 is formed from the mixed and dispersed polyimide solution. Specifically, in a glove box substituted with dry nitrogen having a dew point of −70 ° C. or less, 2 g of calcium oxide powder (or barium oxide powder) is used as the water catching material 16 in 100 ml of a photosensitive polyimide solution (for example, (Trade name: Pymel G-7650E, manufactured by Asahi Kasei Corporation) and stirred to disperse. The glove box in which the polyimide solution has been prepared is degassed at a degree of vacuum of 1 Torr.

As shown in FIG. 1, an organic layer 6 made of a thin film of an organic compound material is laminated on the anode 2. FIG.
Of the organic layer 6 on the anode by PVD method
a CuPc organic film 6a as a hole injection layer formed with a thickness of 10 nm, and an α-NPD organic film 6 as a hole transport layer formed with a thickness of several tens nm on the CuPc organic film 6a.
and a three-layer structure of an Alq ₃ organic film 6c as a light-emitting layer and an electron transport layer formed on the α-NPD organic film 6b with a thickness of several tens of nanometers. Is formed.

As shown in FIG. 1, a metal thin film is formed on the organic layer 6 (Alq ₃ organic film 6c). The metal thin film is made of, for example, a metal material having a small work function, such as Al, Li, Mg, Ag, In, or the like, or an alloy having a small work function, such as Mg: Ag or Al: Li. The metal thin film is formed with a thickness of, for example, several tens to several hundreds of nm by a PVD method,
A cathode 7 is formed as an electrode. Part of the cathode 7 is
It is pulled out to the end of the element substrate 1 and connected to a power supply circuit (not shown).

A sealing substrate 8 as a sealing member is fixed to an outer peripheral portion of the element substrate 1 with an adhesive such as an ultraviolet curing resin. Thus, a package 9 for protecting the element formed on the element substrate 1 is configured. Inside the package 9, for example, nitrogen having a dew point of about -70 ° C,
An inert gas such as helium, neon, or argon, or a low-activity gas such as dry air is sealed as the sealing gas G.

Next, a method of manufacturing an organic EL device having the above-described configuration will be described. First, a transparent conductive film (ITO) is formed to a thickness of about 150 nm on the element substrate 1 by, for example, a sputtering method, and the anode 2 is formed by lamination. The transparent conductive film is formed on the element substrate 2 with the through holes 4 so as to form the light emitting area 3 according to a predetermined pattern.

Next, the element substrate 1 on which the anode 2 having a predetermined pattern shape having the through-holes 4 is formed, is spin-coated with a polyimide solution in which a water trapping material 16 is mixed and dispersed, and is subjected to pre-baking, exposure, development, and post-baking. The order is as follows. As a result, a desired polyimide pattern containing the water catching material 16 is formed on the anode 2.

The polyimide pattern can be formed by a dipping method, a doctor blade method,
It can also be formed using a method such as an applicator method or a transfer method.

Subsequently, the element substrate 1 is subjected to a heat treatment at 300 to 400 ° C. for one hour in an air or nitrogen atmosphere.
As a result, on the anode 2 of the element substrate 1, the through hole 4 is filled and the edge portion 4 a of the through hole 4 is covered, so that the film thickness 1 to 1 of the polyimide film containing the water catching material 16 is formed.
Insulating layer 1 of about 20 μm (preferably 1 to 10 μm)
5 are formed.

Next, the element substrate 1 on which the anode 2 and the insulating layer 15 are laminated is washed (for example, UV ozone washing).
On the cleaned element substrate 1, an organic layer 6 and a cathode 7 are sequentially deposited by resistance heating in a deposition apparatus to form a film. Then, the deposition apparatus is purged with dry nitrogen having a dew point of −70 ° C. or less, and the element substrate 1 is moved to a glove box replaced with the same dry nitrogen without exposing to the atmosphere.

Here, in a step different from the above step, an ultraviolet curable resin as an adhesive is applied to the outer peripheral edge portion of the sealing substrate 8 from which water has been removed by washing in advance. Then, the sealing substrate 8 to which the adhesive has been applied is adhered to the outer peripheral edge portion of the element substrate 1 so as to be cured by ultraviolet rays to fix the space between the element substrate 1 and the sealing substrate 8, and the gas G ( A package 9 in which dry nitrogen is enclosed is formed. Thus, the organic EL device having the configuration shown in FIG. 1 is completed.

The anode 2 of the organic EL device manufactured as described above was connected to the positive electrode and the cathode 7 was connected to the negative electrode. A continuous current was applied by applying a DC voltage to drive the device continuously at a constant current of 10 mA / cm ² . As a result, the light emission state after the lapse of 2000 hours is not different from the initial state, and the light emission area 3 (organic layer 6) and the insulating layer 1
No non-light-emitting portion due to a dark spot appeared from the boundary of No. 5.

On the other hand, when the organic EL element having the structure shown in FIG.
After 500 hours, a non-light-emitting portion due to a dark spot appeared in the light-emitting area.

As described above, according to the above embodiment, the insulating layer 15 is formed by the polyimide film obtained by heat-treating the polyimide solution in which the water trapping material 16 is mixed and dispersed.
Since the water trapping material 16 inside causes a chemical reaction with water to adsorb and hold moisture, it is possible to suppress generation of a non-light emitting portion from a boundary between the insulating layer 15 and the light emitting area 3 (organic layer 6).

As a result, the shape of the light emitting area 3 can maintain the same state as the initial state for a long time. Since the light emitting area of the light emitting area 3 hardly decreases, a voltage increase due to an increase in current density due to a decrease in the light emitting area of the light emitting area 3 can be suppressed, and wasteful power consumption can be reduced.

By the way, in the illustrated example, the CuPc organic film 6a, the α-NPD organic film 6b, the Alq ₃
Although the three-layer structure of the organic film 6c has been described, the organic film 6c is composed of a combination of a light emitting layer and a charge transport layer (a hole transport layer, a hole injection / transport layer, an electron injection layer, an electron injection / transport layer, etc.). be able to.

Specifically, only one light emitting layer, two layers of a light emitting layer and a hole transport layer, two layers of a light emitting layer and an electron injection layer, three layers of a hole transport layer, a light emitting layer and an electron injection layer, and the like. It consists of. In the case where the light emitting layer itself emits light, for example, aluminum quinoline (Alq ₃ ) or a distilylylene-based compound is used as the light emitting material of the light emitting layer. When light emission is performed by doping a small amount of another light-emitting material (dopant) into the light-emitting layer, quinacridone (Qd), a dye for laser, or the like is used as the dopant.

As the electron injection layer, a metal material having a small work function, such as Li, Na, Mg, Ca, or the like, or Al: Li,
An alloy having a small work function such as Mg: In or Mg: Ag is used.

In the above embodiment, the anode 2 made of the transparent conductive film having the through holes 4 is formed on the element substrate 1. However, the anode 2 made of the transparent conductive film and the cathode 7 made of the metal thin film are used. The configuration may be reversed. In this case, since light emission is observed from the anode 2 side, the element substrate 1 does not necessarily need to have a light-transmitting property, and can be formed of a glass substrate having an insulating property.

An anode 2 and a cathode 7 forming a pair of electrodes
It is sufficient that at least one is formed of a conductive material (transparent electrode) having transparency. At this time, when both electrodes are made of a conductive material having transparency, a conductive material having a large work function (ITO) is used for one electrode, and a transparent material having a small work function is used for the other electrode. Use a conductive material having

[0045]

As is apparent from the above description, according to the present invention, the insulating layer is formed to contain the water catching material, and the water catching material in the insulating layer causes a chemical reaction with water to remove water. Since the holding is performed by suction, generation of a non-light emitting portion from the boundary between the insulating layer and the light emitting area can be suppressed.

As a result, the shape of the light emitting area can maintain the same state as the initial state for a long time. And
Since the light emitting area of the light emitting area hardly decreases, a voltage increase due to an increase in current density due to a decrease in the light emitting area of the light emitting area can be suppressed, and wasteful power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of an organic EL device according to the present invention.

FIG. 2 is a side sectional view showing a configuration of a general organic EL element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Element board, 2 ... Anode, 3 ... Light-emitting area, 4 ... Through-hole,
4a: edge portion, 5: insulating layer, 6: organic layer, 7: cathode, 8: sealing substrate, G: sealing gas.

Claims (4)

[Claims] 1. An element substrate, a first electrode formed of a conductive film having a through hole so as to form a pattern of a light emitting area, and formed of a conductive film formed on the element substrate; An insulating layer formed on the first electrode so as to cover an edge portion of the hole; an organic layer including a light emitting layer formed on the first electrode and the insulating layer; An organic EL device comprising: a second electrode made of a conductive film formed thereon; and a sealing member sealed to an outer peripheral portion of the element substrate while the inside is kept in a dry atmosphere. An organic EL device comprising a layer containing a water catching material. 2. The organic EL device according to claim 1, wherein at least one of the two electrodes is made of a conductive film having transparency. 3. The organic EL device according to claim 1, wherein the insulating layer is formed of a polyimide film obtained by heat-treating a polyimide solution in which a water catching material is mixed and dispersed. 4. The organic E according to claim 1, wherein the water catching material is made of calcium oxide or barium oxide.
L element.